Circuit interrupter with improved contact structure

ABSTRACT

A circuit interrupter, such as a circuit breaker, comprising a relatively stationary contact structure which is adapted to be engaged by movable contact means mounted on a pivotally mounted switch or contact arm.

United States Patent Fred Bould;

Richard Hauser, Pittsburgh, Pa. 770.297

Oct. 24, 1968 Feb. 9, 197 1 Westinghouse Electric Corporation Pittsburgh, Pa.

a corporation of Pennsylvania Inventors Appl No. Filed Patented Assignee CIRCUIT INTERRUPT ER WITH IMPROVED CONTACT STRUCTURE 7 Claims, 7 Drawing Figs.

U.S. CI 200/146, 200/ 1 66 Int. Cl H01h 9/38, H0111 33/12 Field of Search 200/ 146, 150.5, 166D, 166E [56] References Cited UNITED STATES PATENTS 2,426,387 8/1947 Caswell 200/146 3,210,506 10/1965 Frink 200/146 3,287,534 11/1966 Cellerini et a1. 200/168(A) 3,328,550 6/1967 Miller 200/166(E) 3,345,485 10/1967 Engle 200/146 3,402,274 9/1968 Bould 200/146 Primary Examiner-Robert S. Macon Attorneys-A. T. Stratton and C. L. Mc Hale ABSTRACT: A circuit interrupter, such as a circuit breaker, comprising a relatively stationary contact structure which is adapted to be engaged by movable contact means mounted on a pivotally mounted switch or contact arm.

PATENTEU FEB 9 [SH 3,562,459 SHEEI1UF3 FIG. I.

INVENTORS Fred Bould and Richard House! ATTORNEY PATENTED FEB 919m 3.562.459 SHEET 3 OF 3 CROSS REFERENCES TO RELATED APPLICATIONS Certain inventions disclosed in the present application are disclosed and claimed in copending application Ser. No. 770,149 filed concurrently with this application by Fred Bould and in copending application Ser. No. 538,996 filed March 3], 1966 by Joseph D. Findley and issued February I l, 1969 as U.S. Pat. No. 3,427,419 which are both assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION This invention relates to circuit interrupters, such as circuit breakers, and more particularly to contact structures which form part of said interrupters. In certain types of circuit interrupters or breakers, a movable contact or switch arm structure having relatively movable main and arcing contact members thereon is pivotally movable to an operating position in which the movable main and arcing contacts engage corresponding relatively stationary main and arcing contact members respectively. Known contact structures of this type are illustrated in U.S. Pat. No. 2,836,684 which issued to H. J. Lingal et al. and in U.S. Pat. Nos. 2,849,579 and 3,210,506 which issued to Russell E. Frink and which are all assigned to the same assignee as the present application. Other contact structures of this type may be found in U.S. Pat. Nos. 3,033,964, 3,215,803 and 3,223,799. These known contact structures when called upon to carry and interrupt relatively high currents, such as 600 or 800 amperes or higher have certain disadvantages with respect to the relative size of the contact structures and with respect to the ease or convenience with which certain contact parts may be removed for replacement or maintenance purposes. It is therefore desirable to provide a circuit interrupter or circuit breaker having improved contact structures which are more compact in construction than known contact structures of the same general type and which are more readily adapted to permit the removal of certain contact parts for replacement or maintenance.

SUMMARY OF THE INVENTION In accordance with the invention, a circuit interrupter or circuit breaker is provided in which a movable contact or switch arm is pivotally supported and is actuable to engage or disengage a relatively stationary contact structure or assembly to open and close the circuit interrupter. The stationary contact assembly includes a pair of electrically conducting outer wall or flat bar members and an additional electrically conducting wall or flat bar member intermediate said outer wall members with a plurality of main stationary contact members disposed between the outer wall members and the additional wall member and pivotally supported on the associated wall members. The main stationary contact members are biased for limited movement relative to the associated wall members by biasing means disposed between the wall members. A pair of relatively stationary arcing contact members are disposed on opposite sides of the additional wall member and biased toward the additional wall member and toward one another by an additional biasing means which permit relative movement of the arcing contact members. In order to open and close the circuit interrupter, a pivotally mounted contact or switch arm having movable main and arcing contact members mounted thereon is actuable by an associated means between a first operating position in which the movable main and arcing contact members engage the stationary main and arcing contact members respectively and a second operating position in which the respective main and arcing contacts of the circuit interrupter are disengaged from each other. In the first operating position of the circuit interrupter, the movable arcing contacts are disposed between the associated pair of stationary arcing contact members. In one aspect of the invention, the electrically conducting wall members of the stationary contact assembly may be formed as unitary members with one terminal of the circuit interrupter, while the pivotal support :of the contact or switch arm may be formed unitarily with another terminal of the circuit interrupter.

It is therefore an object of this invention to provide a circuit interrupter having an improved contact structure or means.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical sectional view taken through one pole of a circuit interrupter embodying the principles of the invention with the circuit interrupter shown in the closed circuit positron;

FIG. 2 is an enlarged front elevational view of a stationary contact assembly which forms part of the circuit interrupter shown in FIG. 1;

FIG. 3 is an enlarged top plan view of the stationary contact assembly shown in FIG. 2;

FIG. 4 is an enlarged view, partly in side elevation and partly in section, of the stationary contact assembly shown in FIGS. 2 and 3 taken along the line IV-IV of FIG. 3;

FIG. 5 is a front elevational view of a switch or contact arm which forms part of the circuit interrupter shown in FIG. 1;

FIG. 6 is an enlarged view, partly in side elevation and partly in section, of the movable switch or contact arm shown in FIG. 5 and its associated pivotal support; and

FIG. 7 is an enlarged top plan view of the movable switch or contact arm and the associated support shown in FIGS. 5 and 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and FIG. 1 in particular. there is illustrated a circuit interrupter, more specifically a circuit breaker l0, embodying the principles of the invention. The circuit breaker 10 may be of the type which is disclosed in greater detail in copending application Ser. No. 770,296 filed concurrently by by F. Bould, R. Hauser and .I. H. Taylor which is assigned to the same assignee as the present application. The circuit breaker 10 may be of the drawout type and may be mounted on a rigid frame which supports the elements of the circuit breaker 10 and which may be provided with rollers to facilitate rolling the circuit breaker 10 into and out of an associated cubicle or cell in order to connect and disconnect the circuit breaker 10 in an electrical circuit.

In general, the circuit breaker 10 includes an electrically insulating base member 70 which is rigidly supported on the framework (not shown) of the circuit breaker 10 along with other pole units similar to the circuit breaker 10 as disclosed in greater detail in the last-mentioned copending application. The circuit breaker 10 also includes a stationary contact assembly 20 which is rigidly supported on the insulating base member 70 and which may include portions which serve as the upper terminal of the circuit breaker 10. In addition, the circuit breaker 10 includes a movable switch or contact arm 30 having movable main and arcing contact members mounted thereon which is pivotally supported on a hinge membei or pivot support member 40 which, in turn, is rigidly supported on the insulating base member 70 and which may include portions which serve as the lower terminal of the circuit breaker 10 as viewed in FIG. 1. As shown in FIG. I, the circuit breaker 10 may also include a pair of spaced upper and lower disconnecting contact assemblies 60 which are removably assembled on the upper and lower terminals, respectively, of the circuit breaker l0 and which are adapted to engage the upper and lower electrical conductors 122 and 124, respectively, in order to electrically connect the circuit breaker 10 to the bus bars or electrical power conductors of an associated switchgear structure (not shown) which may include a cell or housing in which the circuit breaker 10 is normally disposed. The disconnecting contact assembly 60 may be of the type which is described in detail in copending application Ser. No. 538,996 previously mentioned.

More specifically, the stationary contact assembly 20, as best shown in FIGS. 2 through4, includes a plurality of support members or strap members 32, 34 and 36 which are formed from a material having a relatively high electrical conductivity, such as silver plated copper. The right-hand portions of the support or wall members 32, 34'and 36, as indicated at 32C, 348 and 36C, respectively, in FIG. 3, are disposed in tightly assembled relationship and secured or clamped together by suitable means, such as a plurality of spaced rivets 42, with'the right-hand portions of said support members extending through a common opening in the upper portion 70A of the insulating base member 70 and projecting away from the rear side ofthe insulating base member 70, as shown in FIG. 1, to form the upper terminal of the circuit breaker on which a disconnecting contact assembly 60 is assembled. The right-handportions 32C and 36C of the outer support members 32 and 36, respectively, each includes a plurality of openings, as indicated at 36Din FIG. 4, for the support member 36 which are adapted to receive portions of the contact fingers which form part of .theupper disconnecting contact assembly 60, as described in detail in the copending application Ser. No. 538,996 previously mentioned, in order to retain the upper disconnecting contact assembly 60in assembled relation with the upper terminal of the circuit breaker 10 which is formed by the portions of the support members 32, 34 and 36 just described. The left-hand portions 32A and 36A of the outer pair of support members 32 and 36 respectively are offset in opposite directions from the associated right-hand portions 32C and 36C and spaced away from the left-hand portion 34A of the central or intermediate support member 34 in opposite directions, asbest shown in FIG. 3, with the left-hand portions 32A and 36A of the support members 32 and 36 respectively being interconnected to the as sociated right-hand portions 32C and 36C respectively by the intermediate portions 328 and 368, respectively which extend or project away from the intermediate support member 34 in opposite directions generally transversely with respect to said intermediate support member.

In order to removably secure the stationary contact assembly to the upper portion 70A of the insulating base member'70, the intermediate portions 328 and 36B of the outer support members 32 and 36, respectively, include respective openings in which part of suitable fastening means, such as the nuts 132 and 136, respectively, are rigidly retained by suitable means, such as press fitting. As best shown in FIG. 1, when the stationary contact assembly 20 is assembled on the upper portion'70A of the insulating base member 70, a

pair of bolts 122 are assembled through substantially aligned openings in the upper portion 70A and the intermediate portions 32B and 36B of the support members 32 and 34, respectively, to engage the associated nuts 132 and 136, respectively. The bolts 122 are then tightened down until the intermediate portions 32B and 36B bear against the upper portion 70A of the insulating base member 70, as shown in FIG. 1. It is important to note that the stationary contact assembly 20 may be readily removed from the insulating base'member 70 by simply loosening the two bolts 122 and the entire stationary contact assembly 20 may then be readily removed from the insulating base member 70. It is also to be noted that the nuts 132 and 136 are preferably formed from a material, such as steel, having a relatively higher structural strength than the material from which the support members 32 and 34 are formed.

In order to pivotally support a plurality of laterally spaced main stationary contact members 72 in the two compartments or overall cage formed between the central or intermediate support member 34 and the outer pair of support members 32 and 34 at the front side of the upper wall portion 70A of the insulating base member 70, a pivot pin or bolt 84 is disposed to pass through substantially aligned openings in the support members 32, 34 and 36 generally transversely with respect to said support members. Suitable means, such as a lock nut 88, may be disposed on the end of the bolt 84 away from the head of the bolt 84 at one side of the stationary contact assembly and 36.

20, as best shownin FIG. 2. Each of the main stationary contact members'72 is fonned from a material having a relatively high electrical conductivity such as a silver'plated copper arid each of said contact membersincludes'a main stationary contact surface 72A'which ispositioned to be engaged by the movable main contact means, as will be described hereinafter, and is preferably formed from an electrically conducting material having'a'greate'r' wearing ability in service, such as a silver-tungsten alloy. It is to be noted that the contact mem bers 72 include substantially aligned openings through which the bolt 84 also passes and that said contact members are pivotally supported for movement in planes which are generally parallel to the-associated support members 32, 34

In order to provide an efficient current carrying path between the main stationary contact members 72 and the adjacent elect'rically conducting support'mernbe'rs 32, 34 and 36, an electrically conducting bearing tube 114 is disposed around the intermediate portion of the bolt 84 and extends transverse- Iybetween the outer support'membe'rs 32 and 34 as best indicated in FIG. 2. The bearing tube 114 is preferably formed from a material having a'relatively high electrical conductivity such as silver plated copper. In order to insure proper spacing of the contact member 72'al ong the axis of the bearing tube 114, a plurality of ringshaped spacers 115 may be disposed between certain pairs of main stationary contact members 72. as best shown in FIG. 2. v

In order to insure'adequate'contact pressure between the contact members 72 and the associated movable main contact means mounted on the contact or switch arm 30, which will be described hereinafter, and to insure contact follow when the circuit breaker 10 opens, suitable biasing means is disposed between the intermediate support member 34 and each of the outer support members 32' and 36 as best shown in FIGS. 3 and 4. As illustrated, a compression spring 102 is disposed between a spring seat or guide 128 which bears against one of the intermediate portions"32B or 368 of the outer support members 32 and 36, respectively, and a pair of the contact members 72." Each of the contact members 72 may include a recess which is adapted to receive the end of the associated compression spring 102' and'each contact member 72 may include a projecting portion 728 which bears against one end of the associated compression spring 102 to assist in equalizing the pressure or force exerted on each contact member 72 which is biased by a particular compression spring 102. It is also important to note that the compression springs 102 also insure adequate contact pressure between each of the contact members 72' and the bearing tube 114 by biasing the upper end of each contact member 72 around the opening through which the bearing tube 114 passes against the bearing tube 114. 1 I

In order to substantially prevent each of the compression spring 102 from moving out of position either laterally or in a direction transverse to the axis of a particular compression spring 102, the spring guide members 116 and 118' are disposed between each pair of compression springs 102 on opposite sides of the'centr'al support member 34as shown in FIGS. 3 and 4. In order to retain each of the spring guide members 116 and 118 in assembled relationship and inproper position, each of said spring guide members includes a slot at the front end thereof which bears against the bearing tube 114, while the other end of each spring guide member projects through substantiallyaligned openings in one of the spring seats 128 and in the adjacent intermediate portions 1328 and 136B of the outer sup'port members 32 and 36, respectively. Since the opening in the spring seats 128 through which the associated spring guides 116 and 118 pass are close fitting, the springguides 116 andil18 assist'in properly positioning the spring seats 128 within the stationary contact assembly 20.

In order to limit the pivotal or rotational movement of the contact member 72 about the associated bolt 84, each of the contact members 72 includes a recess, as indicated at 72C in FIG. 4, which is located at the bottom end of each contact member 72. A common stop pin 83 is disposed to pass through substantially aligned openings provided in the support members 32, 34 and 36 with the back edge of the recess 72C in each contact member 72 disposed to bear against the stop pin 83 under the influence of the associated biasing spring 102 when the circuit breaker is in the open circuit condition which corresponds to the position of the parts of the stationary contact assembly shown in FIG. 4. In other words, the stop pin 83 limits clockwise movement of each contact member 72 under the influence of the associated compression spring 102 when the circuit breaker 10 is in the open position. When the circuit breaker 10 is in the closed position shown in FIG. 1, the stop pin 83 is disposed intermediate the front and back edges of the recess 72C in each of the contact members 72. It is to be noted that the bearing tube 114 which is disposed on the pivot bolt 84 between the outer support members 32 and 34 also acts as a spacer member to substantially prevent over tightening of the nut 88 which is disposed at one end of the bolt 84 in order to avoid any interference with the free rotation of the contact members 72 during the operation of the circuit breaker 10.

In order to support a pair of arcing contact members 52 and 54 on opposite sides of the intermediate support member 34 between the intermediate support member 34 and each of the adjacent outer support members 32 and 34, respectively, as best shown in FIGS. 2 and 3, a support pin or bolt 82 is disposed to pass through substantially aligned openings provided in the support members 32, 34 and 36 and in the arcing contact members 52 and 54 generally transversely with respect to the support members 32, 34 and 36 with suitable means being provided to retain the bolt 82 in assembled relation with the associated parts of the stationary contact assembly 20, such as a lock nut 86 which is disposed at the end of the bolt 82 away from the head thereof. In order to establish adequate contact pressure between the stationary arcing contact members 52 and 54 and the movable arcing contact means which is disposed on the movable contact or switch arm 30, as will be described hereinaftenthe compression springs 92 and 94 are disposed on the pivot bolt 82 between the intermediate portion of the associated stationary arcing contact members 52 and 54 respectively and the adjacent outer support members 32 and 36, respectively, as best shown in FIG. 3. The compression springs 92 and 94 bias the arcing contact members 52 and 54 toward the intermediate support member 54 and toward each other but permit lateral separating movement of the contact members 52 and 54 toward and away from each other during the operation of the circuit breaker 10 as will be described hereinafter. The arcing contact members 52 and 54 are formed from a material having a relatively high electrical conductivity such as silver plated copper and include the arcing contact inserts or surfaces 62 and 64, respectively, which are located adjacent the outer ends of said arcing contact members with the arcing contact surfaces 62 and 64 facing each other, as best shown in FIG. 3, but being laterally spaced from each other a predetermined distance when the circuit breaker 10 is in the open position which corresponds to the position of the parts shown in FIG. 3.

It is to be noted that the arcing contact members 52 and 54 include the first generally arcuate or curved portions 52A and 54A, respectively, which bear against the intermediate support member 34 which acts as a stop member to limit the movement of the arcing contact members 52 and 54 toward each other under the influence of the compression springs 92 and 94 when the circuit breaker 10 is in the open circuit condition. The arcing contact members 52 and 54 also include the second generally arcuate or curved portions 52B and 548, respectively, adjacent the ends of said contact members away from the arcing contact surfaces 62 and 64 with the generally arcuate portions 528 and 54B acting as fulcrums or pivot surfaces when the arcing contact members 52 and 54 are actuated farther apart during the operation of the circuit breaker 10 as will be explained hereinafter. In order to guide the lateral movement of the arcing contact members 52 and 54 away and toward each other during the operation of the circuit breaker 10, the guide pin is disposed to extend generally transversely between the outer support members 32 and 36 as best shown in FIG. 3'with the guide pin 85 passing through substantially aligned openings in the support members 33, 34 and 36 and through the slots provided at the adjacent ends of the arcing contact members 52 and 54 as indicated at 54B in FIG. 4 for the arcing contact member 54 to permit the relatively separating and closing or approaching movements of the arcing contact members 52 and 54 during the operation of the circuitbreaker 10. Each of the arcing contact members 52 and 54 also includes an arc runner portion, as indicated 54A for the arcing contact member 54 in FIGS. 1 and 4, which assist in carrying the arcing current which results during the operation of the circuit breaker I0 up into an associated arc extinguishing structure, such as disclosed in copending application Ser. No. 800,106 which is assigned to the same assignee as the present application. It is to be noted that when the circuit breaker 10 is in the closed position, a current transfer path is established between the arcing contact members 52 and 54 and the intermediate electrically conducting support member 34 through the generally arcuate portions 52B and 54B and the portion of the intermediate support member 34 which are in contact with said generally arcuate portions of said arcing contact members.

In order to pivotally support the switch or contact arm 30 at a location which is vertically spaced from the stationary contact assembly 20 just described, the pivot support or hinge member 40 is secured to the lower portion 705 of the insulating base member 70. As best shown in FIGS. I and 7, the hinge member 40 includes a pair of support members 232 and 234 which are formed from a material having a relatively high electrical conductivity such as silver plated copper. The support members 232 and 234 include the right-hand portions 232C and 234C, respectively, as viewed in FIG. 7 which extend through a common opening in the insulating base member 70 and are disposed in tightly assembled relationship with the right-hand portions 232C and 234C being secured or clamped together by suitable means such as a plurality of spaced rivets 297, as shown in FIGS. 6 and 7, to form a lower tenninal of the circuit breaker 10 on which the lower disconnecting contact assembly 60 is assembled as shown in FIG. I. Similarly to the support members 32 and 36 previously described, each of the support members 232 and 234 include a plurality of openings as indicated at 234D in the right-hand portion 234C, which are adapted to receive portions of the contact fingers which form part of the lower disconnecting contact assembly 60 and to assist in retaining the disconnecting contact assembly 60 in assembled relation with the lower terminal of the circuit breaker 10 which is formed by the support members 232 and 234, as described in greater detail in copending application Ser. No. 538,996 previously mentioned.

In order to rigidly secure the support or hinge member 40 to the lower portion 708 of the insulating base member 70. the intermediate portions 2328 and 2348 of the support members 232 and 234 respectively which extend generally transversely with respect to the right-hand portions 232C and 234C respectively of said support members include openings: in which are secured parts of suitable fastening means such as the nuts 276 and 278 shown in FIGS. 6 and 7 which are rigidly secured in said openings by suitable means such as press fitting. When the hinge member 70 is mounted on the insulating base member 70, a pair of bolts 279 as shown in FIG. 1 are assembled through substantially aligned openings in the lower portion 70B of the insulating base member 70 and the intermediate portions 232B and 234B of the support members 232 and 234 respectively with the ends of the bolts 279 away from the heads thereof engaging the nuts 276 and 278. The bolts 279 are then tightened down until the intermediate portions 232B and 2348 of the support members 232 and 234 respectively bear against the lower portion 70B of the insulating base member 70 as shown in FIG. 1. As shown in FIG. 7, the lefthand or hinge portions of the support members 232 and 234, as indicated at 232A and 234A, respectively, are offset or laterally spaced in opposite directions from the associated right-hand portions 232C and 234C, respectively, which are interconnected to the hinge portions by the intermediate portions 232B and 2348, respectively.

In order to pivotally support the switch or contact arm 30 on the support or hinge member 40, a pivot bolt or pin 268 is provided which passes through substantially aligned openings in the hinge portions 232A and 234A of the support member 40 and extends across the space between said hinge portions, as best shown in FIG. 7. The pivot bolt 268 may be retained in assembled relation with the hinge member 70 by suitable means such as the nut 269 which is disposed on the pivot bolt 268 at the end of said bolt away from the head thereof.

As best shown in FIG. 5, the switch or contact arm 30 includes a pair of generally U-shaped contact support members 220 and 240 which are disposed in generally nested relation with the contact support member 240 being disposed inside the contact support member 220 and with both of said contact support members 220 and 240 being pivotally supported on the pivot bolt 268. Both of the contact support members 220 and 240 are formed from a material having a relatively high electrical conductivity, such as silver plated copper; The support member 220 includes a pair of spaced arms 220A and 220C which are interconnected by a yoke or bight portion 220B. Similarly, the support member 240 includes a pair of spaced arms 240A and 240C which are interconnected by a yoke or bight portion 240B. The arms 220A and 220C of the contact support member 220 are assembled on the pivot bolt 268 adjacent the outer sides of the hinge portions 232A and 234A respectively of the support members 232 and 234 respectively with the pivot bolt 268 passing through substantially aligned openings in said arms adjacent the ends of said arms away from the associated bight portion 220B. The arms 220A and 2203 include the raised contact portions or bosses 220D and 220E, respectively, around the openings through which the pivot bolt 268 passes, as best shown in FIG. 5. The raised contact portions 220D and 220E bear against or engage the adjacent hinge portions 232A and 234A, respectively. In order to insure adequate contact pressure between the contact portions 220D and 220E and the hinge portions 232A and 234A, the spring washer washers 254 and 256 are disposed on the bolt 268 and the arm 220A of the contact support member 220 and the spring washer 256 being disposed between the nut 269 and the arm 220C of .the support member 220 as best shown in FIG. 5. In order to prevent overtightening of the nut 269 which might interfere with the free rotation of the support members 220 and 240, a generally tubular spacer member 266 is disposed on the intermediate portion of the bolt 268 and extends generally transversely between the hinge portions 232A and 234A and into the substantially aligned openings of said hinge portions.

Similarly, the arms 240A and 240C includes raised contact portions or bosses 240D and 240E around the openings through which the bolt 268 passes with the raised contact portions 240D and 2405 bearing against or engaging the inner sides of the hinge portions 232A and 234A respectively between which the arms 240A and 240C are disposed. In order to insure adequate contact pressure between the raised contact portions 240D and 240E on the support member 240 and the adjacent inner sides of the hinge portions 232A and 234A, respectively, the compression spring 242 is disposed on the bolt 268 around the tubular spacer member 266 as shown inFIG. S and serves to bias the raised contact portions 240D and 240E against the adjacent hinge portions 232A and 234A, respectively. The arms of the contact support members 220 and 240 must be sufficiently resilient to permit deflection of the lower ends of the arms of the contact support member 220 and 240 into engagement with the hinge portions 232A and 234A under the influence of the spring washers 254 and 256 and the biasing spring 242. It is to be noted that in certain applications where the additional current carrying capacity of the contact support member 240 is not required, the contact support member 240 may be omitted along with the compression spring 242 with such a construction including only the contact support member 220 as previously described.

The movable; main contact member or block 250, as best shown in FIGS. 5 and 6, is mounted or supported on the bight portions 2208 and 2408 of the support members 220 and 240 respectively and is disposed to follow a generally arcuate path about the axis of the bolt 268 when the support members 220 and 240 are actuated for rotation about the bolt 268. The movable main contact member 250 is formed from a-material having a relatively high electrical conductivity, such as silver plated copper, and includes a main contact surface or insert 252, as shown in FIGS. 6 and 7, which is formed from a material having greater wearing ability than the material from which the main contact member 250 is formed, such as a silver-tungsten alloy. It is to be noted that the main contact member 250 extends substantially across the width of the switch or contact arm 30, as shown in FIG. 5, along with the main contact surface 252 which is disposed to engage the corresponding stationary main contact surface 72A on each of the stationary main contact members 72 which form part of the stationary contact assembly previously described in a butt type contact arrangement when the circuit breaker 10 is closed as shown in FIG. I.

The switch or contact arm 30 also includes a pair of arcing contact members 262 and 264, as best shown in FIG. 5, which are mounted on top of the movable main contact member 250 and supported on the bight portions 2208 and 2408 of the support members 220 and240, respectively, with the arcing contact members 262 and 264 extending or projecting radially away from the axis defined by the bolt 268. The movable arcing contact members 262 and 264 are generally L-shaped in configuration and are formed from a material having a relatively high electrical conductivity, such as copper. The movable arcing contact members 262 and 264 include the foot portions 262A and 264A, respectively, which are secured to the bight portions 2208 and 2408 of the support members 220 and 240, respectively, along with the movable main contact member 250 by a pair of bolts 216 and 218 which pass through substantially aligned openings in the respective foot portions 262A and 264A, as best shown in FIG. 6, the movable main contact member 250 and the bight portions 2208 and 2408 to engage the nuts 212 and 214, respectively, which are rigidly secured in corresponding openings provided in the contact support member 240 with the nuts 212 and 214 being rigidly secured in said openings by suitable means, such as press fitting. The upper portions of the arcing contact members 262 and 264 may also be rigidly secured together by suitable means, such as brazing, or by pins or rivets which pass through substantially aligned openings provided in said arcing contact members. It is important to note that the arcing contact members 262 and 264 along with the movable main contact member 250 may be readily disassembled from the switch or contact arm 30 for replacement or maintenance by loosening only a pair of the bolts 216 and 218 as just described.

A pair of arcing contact surfaces or inserts 272 and 274 are mounted on the upper portions of the movable arcing contact members 262 and 264, as best shown in FIGS. 5 and 6. The arcing contact inserts 272 and 274 are secured to the associated arcing contact members 262 and 264 by suitable means, such as brazing, and are preferably formed from a material having a relatively greater resistance to arcing such as a silver-tungsten alloy having a relatively higher proportion of tungsten. When the circuit breaker 10 is in the closed position, the arcing contact members 262 and 264 are disposed between the stationary arcing contact members 52 and 54 with the arcing contact surfaces 272 and 274 engaging or bearing against the relatively stationary arcing contact surfaces 62 and 64, respectively, which are disposed on the stationary arcing contact members 52 and 54 respectively. It is to be noted that the uppermost portions of the movable arcing contact members 262 and 264 as indicated at 2628 and 2648 are formed as are runners which assist in the movement of the are which normally results during an opening operation of the circuit breaker 10 into an associated arc extinguishing means (not shown) such as disclosed in copending application Ser. No. 800,106 previously mentioned.

In order to actuate the switch or contact arm 30 between a first position which corresponds to the closed circuit condition of the circuit breaker 10, as shown in solid lines in FIG. 1, and a second position which corresponds to the open circuit condition of the circuit breaker 10, as indicated in phantom at 30' in FIG. I, the movable switch or contact arm 30 is operatively connected by means of an insulating operating member 300 which is pivotally connected at one end to a cross member 310 which extends transversely through substantially aligned openings in the support members 220 and 240 to a suitable operating mechanism which may be of the type disclosed in detail in copending application Ser. No. 770,296 previously mentioned.

Where desired, a current transformer as indicated diagrammatically at 400 in FIG. 1, may be disposed on the lower terminal of the circuit breaker 10 which is formed by the support members 232 and 234, as previously described in the space which results below the upper portion 70A of the insulating base member 70 which is offset from the lower portion 70B of said insulating base member, as described in greater detail in copending application Ser. No. 770,149 filed concurrently with this application by Fred Bould and which is assigned to the same assignee as the present application.

In the operation of the circuit breaker 10 when the switch or contact arm 30 is actuated from the closed position shown in FIG. 1 by the operating mechanism which is operatively connected to the switch or contact arm 30 through the insulating operating member 300, the switch or contact arm 30 is actuated to rotate about the axis defined by the bolt 268 in a generally counterclockwise direction about said axis. It is to be noted when the circuit breaker 10 is in the closed circuit condition shown in FIG. 1, the arcing contact surfaces 62 and 64 on the stationary arcing contact members 52 and 54 are engaged by the corresponding movable arcing contact surfaces 272 and 274, respectively, disposed on the movable arcing contact members 262 and 264, respectively, and that the movable arcing contact members262 and 264 are disposed between the stationary arcing contact members 52 and 54 with said stationary arcing contact members being separated by a spacing greater than that shown in FIG. 3 of the drawings. The separation of the stationary arcing contact members 52 and 54 as previously explained is opposed by the forces or pressures exerted on said stationary arcing contact members by the associated compression springs 92 and 94, respectively, which insure adequate contact pressure between the arcing contact surfaces 62 and 64 and the corresponding movable arcing contact surfaces 272 and 274 respectively. In addition, the main stationary contact surfaces 72A on the plurality of main contact members 72 which form part of the stationary contact assembly are engaged with the movable main contact surface 252 on the main movable contact member 250 in a butt type contact arrangement. It is to be noted that when the circuit breaker 10 is in the closed circuit condition shown in FIG. I, the plurality of contact members 72 are actuated in a counterclockwise direction about the pivot bolt 84 to further compress the biasing springs 102 and that the common stop member 83 shown in FIG. 1 is disposed intermediate the front and back edges of the recess 72C provided in each of the main stationary contact members 72, as shown in FIG. 1.

When the switch or contact arm 30 is actuated from the closed circuit position shown in FIG. 1 during an opening operation of the circuit breaker 10, the switch arm 30 will start to rotate in a counterclockwise direction about the axis defined by the bolt 268. During the initial rotational travel of the switch arm 30, the movable arcing contact surfaces 272 and 274 will remain in engagement with the associated stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 52 and 54, respectively. During the initial rotational travel of theswfich arm 30, the movable main contact member orsurface 252 will also remain in engagement with the main stationary contact surface 72A on each of the contact members 72 since a each of the main stationary contact members 72 will follow the movement of the switch arm 30 for a relatively short distance under the influence of the compression springs 102 which will actuate the main contact members 72 in a clockwise direction about the pivot bolt 84 until the back edge of the recess 72C in each of said contact members engages the common stop member 83. When the contact members 72 engage the stop member 83 during an opening operation of the circuit breaker I0, the movable main contact surface 252 will separate from the stationary main contact surfaces 72A oneach of the contact members 72 and a gap will quickly develop between the corresponding movable and stationary main contact surfaces 252 and 72A respectively. Meanwhile the movable arcing contact surfaces 272 and 274 will temporarily remain in engagement with theirssociated or corresponding stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 52 and 54 respectively to maintain a current carrying path which extends from the upper terminal formed by the support members 32. 34, 36, the arcing contact members 52 and 54, the movable arcing contact members 262 and 264, the movable main contact member 250, and the contact support members 220 and 240 of the switch arm 30 to the hinge portions 232A and 234A which then carry the current to the lower terminal formed by the support members 232 and 234. As the switch arm 30 continues to rotate in a counterclockwise direction about the axis defined by the pivot bolt 268 the movable arcing contact surfaces 272 and 274 will finally separate from the associated stationary arcing contact surfaces 62 and 64 and the arc which normally results will move into an associated arc extinguishing structure where the arc will be finally extinguished or interrupted during the operation of the circuit breaker 10. It is important to note that each of the contact support members 220 and 240 provide a pair of current carrying paths between the movable main contact member 250 and the hinge portions 232A and 234A of the support members 232 and 234, respectively, through the pairs of raised contact portions 220D and 220E and 240D and 240E, respectively. It is to be noted that a wiping action results between the movable arcing contact surfaces 272 and 274 and the associated stationary arcing contact surfaces 62 and 64 as the movable arcing contact members 262 and 264 leave the closed circuit position between the stationary arcing contact members 52 and 54 because of the biasing forces exerted on the stationary arcing contact members by the associated compression springs 92 and 94 respectively. After both the corresponding main and arcing contacts of the circuit breaker 10 separate during an opening operation of the circuit breaker 10, the switch arm 30 will continue to rotate in a counterclockwise direction about the bolt 268 until the switch arm 30 reaches the fully open position indicated in phantom at 30' in FIG. 1.

During a closing operation of the switch arm 30 will initially be in the open circuit positionindicated in phantom at 30 in FIG. I and the position of the parts of the stationary contact assembly 20 which correspond to the open circuit condition of the circuit breaker 10 will be as shown in FIGS. 2 through 4. It is to be noted in FIG. 3 that the stationary arcing contact members 52 and 54 will initially be relatively closer together, as limited by the intermediate support member 34 against which the generally arcuate portions 52A and 54A bear in the open circuit condition of the circuit breaker I0, as shown in FIG. 3. In addition. each of the main stationary contact members 72 will engage the common stop member 83 as shown in FIG. 4 under the influence of the associated biasing springs 102 with the back edge of the recess 72C ineach of the contact members 72 bearing against the common stop pin 83, as shownin FIG. 4. As the switch arm 30 is actuated from the open circuit position shown in phantom in FIG. I by the operating mechanism of the circuit breaker I0 through the insulating operating member 300, the switch arm circuit breaker I0, the

30 will rotate in a clockwise direction from the open circuit position indicated in phantom about the pivot bolt 268. During the final portion of the rotational travel of the switch arm 30 during closing operation, the movable arcing contact surfaces 272 and 274 on the movable arcing contact members 262 and 264, respectively, will first engage the corresponding stationary arcing contact surfaces 62 and 64 on the stationary arcing contact members 52 and 54 to establish a current carrying path between the upper and lower terminals of the circuit breaker through the various parts previously explained during the opening operation previously described prior to the time that the movable main contact member 250 and the movable main contact surface 252 thereon engages the stationary main contact surfaces 72A on the main stationary contact members 72. As the switch arm 30 is rotated further in a clockwise direction after the movable arcing contact surfaces 272 and 274 first engage the associated stationary arcing contact members 52 and 54 at the stationary arcing contact surfaces 62 and 64, the stationary arcing contact members 52 and 54 will be wedged or pushed farther apart than the spacing shown in FIG. 3 with the stationary arcing contact members pivoting about the generally arcuate contact portions 528 and 543 respectively until the movable arcing contact members 262 and 264are fully engaged with the stationary arcing contact members 52 and 54 and disposed between said stationary arcing contact members as shown in FIG. 1. Any initial arcing wnich takes place at the separable contacts of the circuit breaker 10 will therefore take place between the movable arcing contact surfaces 272 and 274 and the corresponding stationary arcing contact surfaces 62 and 64 respectively, which are mounted on the stationary arcing contact members 52 and 54, respectively to avoid any pitting or wearing of the movable and stationary main contact members of the circuit breaker 10. As mentioned previously, the separating movement of the stationary arcing contact members 52 and 54 is guided at the ends away from the arcing contact surfaces 62 and 64 by the guide pin 85. It is to be noted that a wiping action will take place between the movable arcing contact surfaces 272 and 274 and the corresponding stationary arcing contact surfaces 62 and 64 during a closing operation of the circuit breaker 10.

Subsequent to the initial establishment of a current carrying path between the arcing contact members of the circuit breaker 10 as just described, the movable main contact surface 252 on the movable main contact member 50 will engage the plurality of stationary main contact surfaces 72A on the plurality of main contact members 72 in a butt type contact arrangement and the main contact members 72 will be actuated in a counterclockwise direction about the pivot bolt 84 during a closing operation against the biasing forces exerted on the contact member 72 by the compression springs 102 until the contact members 72 reach the closed circuit position indicated in FIG. 1. It is to be noted that the common stop pin 83 as previously mentioned will be disposed intermediate the front and back edges of the recess 72C at the bottom end of each main stationary contact member 72. When the circuit breaker 10 is in the closed circuit condition shown in FIG. 1, it is to be noted that most of the current which flows between the upper terminal formed by the support members 32, 34 and 36 and the lower terminal formed by the support members 232 and 234 will flow through a current path which includes the main stationary contact members 72 rather than through the electrically parallel current carrying path which includes the stationary arcing contact members 52 and 54 due to the relatively higher resistance which is normally included in the current path which includes the arcing contact members 52 and 54 because of the arcing contact surfaces or inserts 272 and 274 on the switch arm 30 and the arcing contact surfaces or inserts 62 and 64 which are mounted on the stationary arcing contact members 52 and 54 respectively. More specifically, when the circuit breaker 10 is closed most of the current which flows between the upper and lower terminals of the circuit breaker l0 flows from the upper terminal which includes the support members 32, 34 and 36, the electrically conducting bearing tube 114, the pluralit y of main stationary contact members 72, the main stationary contact surfaces or inserts 72A, the main movable contact surface or insert 252 on the switch arm 30, the main movable contact member 250. the contact support members 220 and 240, and the hinge portions 232A and 234A to the support members 232 and 234 which form the lower terminal of the circuit breaker 10.

When the circuit breaker 10 is called upon to carry or interrupt relatively high short circuit or fault currents, the electromagnetic forces which result due to the parallel current paths through the arms of the contact support members 220 ,and 240 of the switch arm 30 increase the contact pressure between the arms of each of the contact support members 220 the opposite sides of each of which the contact arms of said support members are disposed. Similarly, when the circuit breaker 10 is called upon to close against relatively high fault currents, the parallel current paths which result through the pair of stationary arcing contact members 52 and 54 result electromagnetic forces which cause the arcing contact members 52 and 54 to be attracted toward each other and to produce a blowon action at the arcing contact members 52 and 54 during such a closing closing operation. In addition. when the circuit breaker 10 is called upon to carry relatively high short circuit or fault currents, the current path which extends from the contact support members 220 and 240 through the main movable contact member 250 and into the main stationary contact members 72 which are each pivotally supported adjacent to the upper ends thereof includes a current loop which produces electromagnetic forces which tend to actuate each of the contact members 72 in a clockwise direction about the pivot bolt 84 and to actuate the main stationary contact surfaces 72A into engagement with the movable main contact surfaces 252 on the switch arm 30 and thus produce what may be described as a blowon action during such an operating condition.

It is to be understood that the number of main stationary contact members or fingers 72 which are required in a prtrticu lar application may vary in accordance with the current rating of the circuit breaker 10. Similarly, the current carrying capacity of the switch arm 30 may be varied in different applications by varying the number of current carrying paths between themain movable contact member 250 and the hinge portions 232A and 234A by either including or omitting the contact support member 240 where desired for a particular application. In other words, when both contact support members 220 and 240 are provided, four current carrying paths result between the main movable contact member 250 and the hinge portions 232A and 234A or if the contact support member 240 is omitted two current carrying paths will result between said hinge portions and the main movable contact member 250. In addition, the current carrying capacity of the upper and lower terminals may be varied or reduced by modifying the shape of the right-hand portions of the support members which make up the upper and lower terminals to be generally L-shaped rather than generally rectangular, as illustrated and previously described.

The apparatus embodying the teachings of this invention has several advantages. For example, a circuit interrupter or circuit breaker having improved contact means as described is relatively more compact than circuit interrupters employing known contact structures of the same general type. In addition, a stationary contact assembly and a hinge member as disclosed permit the forming of unitary terminal members with the circuit breaker 10 which include support members that form part of the stationary contact assembly or the hinge member 40 as described. A further advantage described is that the different contact structures of the circuit breaker 10 are arranged to take advantage of electromagnetic forces which result during certain operating conditions of the circuit breaker 10 as previously described. Finally, an important advantage of the improved contact structures which form part 01 the circuit breaker 10 is that certain contact parts may be readily removed for replacement or maintenance by the loosening of only two bolts. For example, the entire stationary contact assembly can be readily and conveniently removed from the insulating base member 70 by loosening the pair of bolts 122 which removably secure the stationary contact assembly 20 to the insulating base member 70. Similarly, by loosening only two bolts 216 and 218 on the switch arm 30, both the main movable contact member 250 and the associated arcing contact members 262 and 264 may be readily and conveniently removed forreplacement or maintenance.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in thev accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. An electric circuit interrupter comprising a base member, a stationary contact assembly mounted on said base member, said stationary contact assembly including a pair of spaced, outer electrically conducting wall members and an additional electrically conducting wall member disposed intermediate said outer wall members, a plurality of main stationary contact members disposed between said outer wall members on both sides of said additional wall member and'pivotally supported adjacent corresponding ends on said wall members, means disposed between said additional wall member and said outer wall members for biasing said stationary contact members for limited movement relative thereto, a pair of relatively stationary arcing contact members disposed on opposite sides of said additional wall member, spring means disposed between each of said arcing contact members and the adjacent outer wall member for biasing said arcing contact members toward said additional wall member and toward each other, a movable switch arm pivotally'mounted on said base member and having spaced movable main and arcing contact means disposed thereon, and means for actuating said switch arm between an open position and a closed position in which said movable main and arcing contact members engage said stationary main and arcing contact members, respectively, said movable arcing contact means being disposed between said pair of stationary arcing contact members in the closed position.

2. The combination as claimed in claim 1 wherein a common pivot means extends generally transversely with respect to said wall members through openings in said wall members and said main stationary contact members for pivotally supporting said main stationary contact members and tubular electrically conducting means is disposed on said pivot means to pass through said openings and to form a current carrying path between said wall members and said main stationary contact members.

3. The combination as claimed in claim 3 wherein a common stop member extends generally transversely with respect to said wall members to limit the movement of said main stationary 'contact members during the operation of said circuit interrupter. I 1 1 4. The combination as claimed in claim 1 wherein said switch arm comprises a generally U-shaped electrically conducting member having a bight portion and a pair of spaced 14 arms, said arms being pivotally supported adjacent the end away from said bight portion, a main contact membt' mounted and extending substantially across said bight portio and arcing contact means mounted on said contact membt and extending away from said bight portion. and commi fastening means removably securing said main contat member and said arcing contact means to said bight portion.

5. The combination as claimed in claim 2 wherein sai switch arm comprises a generally U-shaped electrically con ducting member having a bight portion and a pair of spacer arms, said arms being pivotally supported adjacent the end away from said bight portion, a main contact membei mounted and extending substantiall across said bight portioi and arcing contact means mounte on said contact membei and extending away from said bight portion. and commoi fastening means removably securing said main contac' member and said arcing contact means to said bight portion.

6. A circuit breaker comprising an insulating base membe having at least one opening therethrough, a stationary contac assembly mounted on said base member and including a fin support member of conducting material disposed general] transversely with respect to said base member and extendin through said opening, a pair of support members of conduc ing material disposed on opposite sides of said first suppo member and each having a first portion extending throng said opening and being secured to an adjacent portion of sai first support member to form therewith a first terminal meal on one side of the base member, each support member of sai pair including a second portion interconnected with the a: sociated first portion and offset therefrom in oppositdirections from said first support member, said second per tions of said support member and said first support membc projecting away from the other side of said base member, pivot support member mounted on said first support membci and the second portions of saidpair of support members and extending through openings in support members generall transversely thereto, a plurality of main relatively stationar contact member s pivotally mounted on said pivot suppon member between the second portions of said pair of support members for movement generally parallel to said second portions, a pair of relatively stationary arcing contact memben disposed on opposite sides of said first support member between said second portions for relative movement away and toward each other, a movable switch arm pivotally supportet on said base member and having movable main and arcin; contact members thereon and means for actuating said switcl arm to a position in which said main and arcing contact mem bers on said switch arm engage said stationary main and arcin 1 contact members, respectively.

7. The combination as claimed in claim 5, wherein saiswitch ann comprises a generally U-shaped electrically con ducting member having a bight portion and a pair of space arms, said arms being pivotally supported adjacent the end away from said bight portion, a main contact membc mounted and extending substantially across said bight portio and arcing contact means mounted on said contact membrand extending away from said bight portion, and commo: fastening means removably securing said main contat member and said arcing contact means to said bight portion. 

1. An electric circuit interrupter comprising a base member, a stationary contact assembly mounted on said base member, said stationary contact assembly including a pair of spaced, outer electrically conducting wall members and an additional electrically conducting wall member disposed intermediate said outer wall members, a plurality of main stationary contact members disposed between said outer wall members on both sides of said additional wall member and pivotally supported adjacent corresponding ends on said wall members, means disposed between said additional wall member and said outer wall members for biasing said stationary contact members for limited movement relative thereto, a pair of relatively stationary arcing contact members disposed on opposite sides of said additional wall member, spring means disposed between each of said arcing contact members and the adjacent outer wall member for biasing said arcing contact members toward said additional wall member and toward each other, a movable switch arm pivotally mounted on said base member and having spaced movable main and arcing contact means disposed thereon, and means for actuating said switch arm between an open position and a closed position in which said movable main and arcing contact members engage said stationary main and arcing contact members, respectively, said movable arcing contact means being disposed between said pair of stationary arcing contact members in the closed position.
 2. The combination as claimed in claim 1 wherein a common pivot means extends generally transversely with respect to said wall members through openings in said wall members and said main stationary contact members for pivotally supporting said main stationary contact members and tubular electrically conducting means is disposed on said pivot means to pass through said openings and to form a current carrying path between said wall members and said main stationary contact members.
 3. The combination as claimed in claim 3 wherein a common stop member extends generally transversely with respect to said wall members to limit the movement of said main stationary contact members during the operation of said circuit interrupter.
 4. The combination as claimed in claim 1 wherein said switch arm comprises a generally U-shaped electrically conducting member having a bight portion and a pair of spaced arms, said arms being pivotally supported adjacent the ends away from said bight portion, a main contact member mounted and extending substantially across said bight portion and arcing contact means mounted on said contact member and extending away from said bight portion, and common fastening means removably securing said main contact member And said arcing contact means to said bight portion.
 5. The combination as claimed in claim 2 wherein said switch arm comprises a generally U-shaped electrically conducting member having a bight portion and a pair of spaced arms, said arms being pivotally supported adjacent the ends away from said bight portion, a main contact member mounted and extending substantially across said bight portion and arcing contact means mounted on said contact member and extending away from said bight portion, and common fastening means removably securing said main contact member and said arcing contact means to said bight portion.
 6. A circuit breaker comprising an insulating base member having at least one opening therethrough, a stationary contact assembly mounted on said base member and including a first support member of conducting material disposed generally transversely with respect to said base member and extending through said opening, a pair of support members of conducting material disposed on opposite sides of said first support member and each having a first portion extending through said opening and being secured to an adjacent portion of said first support member to form therewith a first terminal means on one side of the base member, each support member of said pair including a second portion interconnected with the associated first portion and offset therefrom in opposite directions from said first support member, said second portions of said support member and said first support member projecting away from the other side of said base member, a pivot support member mounted on said first support member and the second portions of said pair of support members and extending through openings in support members generally transversely thereto, a plurality of main relatively stationary contact members pivotally mounted on said pivot support member between the second portions of said pair of support members for movement generally parallel to said second portions, a pair of relatively stationary arcing contact members disposed on opposite sides of said first support member between said second portions for relative movement away and toward each other, a movable switch arm pivotally supported on said base member and having movable main and arcing contact members thereon and means for actuating said switch arm to a position in which said main and arcing contact members on said switch arm engage said stationary main and arcing contact members, respectively.
 7. The combination as claimed in claim 5, wherein said switch arm comprises a generally U-shaped electrically conducting member having a bight portion and a pair of spaced arms, said arms being pivotally supported adjacent the ends away from said bight portion, a main contact member mounted and extending substantially across said bight portion and arcing contact means mounted on said contact member and extending away from said bight portion, and common fastening means removably securing said main contact member and said arcing contact means to said bight portion. 